Thursday, 29 September 2011

News in Brief #1

Sometimes weeks go by and I have difficulty finding anything very new to post, at least that isn't too similar to something else I've already done recently. Just as often, though, I have to pick between a number of possible stories, and some end up being pushed to the back of the queue, and never leave it. So, every couple of months or so, I'm going to gather up stories that didn't quite make it, and post a short summary here. So, without any more ado:

Are Foreign Mating Calls Still Sexy?

Sika deer

Mating calls are hardly an unusual feature in mammals, and deer are no exception, especially where the males like to gather a larger number of females around them to mate with. You'd think that part of the point of a mating call is to attract females of your own species, so that you end up with a suitable partner. A group of British, Austrian, and French scientists recently tested this out with female red deer (this is the European version of the animal Americans call an 'elk'). They put up loudspeakers emitting recordings of male red deer, and of male sika deer, a closely related Japanese species with similar mating habits, but that looks quite different.

Sure enough, most of the females wandered over to where the calls of the male red deer seemed to be coming from. But ten percent of the females actually seemed to prefer the calls of the sika males, apparently finding them more enticing than the ones from their own males. The researchers say that this may lead to "permeability of pre-zygotic reproductive barriers"... by which they mean a willingness to have sex with the wrong species. And, indeed, after sika deer were introduced into parks in Europe, some hybrids between the two have been reported. Some red deer does, it seems, just find the exotic attractive.

The Insightful Elephant
We've known for a while that we aren't the only species to use tools, even if we ignore instinctive use of objects - such as birds smashing open snails on rocks. Chimpanzees, for example, have the intelligence to work out how to use simple tools to acquire food, and, outside the world of mammals, even some species of crow have been shown to do the same. Elephants seem a reasonable candidate for another animal that might do the same. They are intelligent animals, and they have a trunk that can pick up and manipulate objects.
With this in mind, researchers from the City University of New York tried to persuade Indian elephants to demonstrate insightful problem solving. Having failed to persuade some Indian elephants to do the obvious primate thing and use sticks to pull down food that was otherwise out of reach, they instead gave them objects they could move into position and stand on, and reach the food that way. Yes, its so basic that it hardly qualifies as a tool, but the fact that one of the males worked out (without any prompting) that this technique would work, shows a degree of problem solving ability not normally seen in non-primate species. He was able to generalise the idea to various other objects, even stacking objects on top of one another when they were not large enough on their own.

Obviously, we can't know exactly what was going on in his mind, but this presumably wouldn't be something he'd normally do in the wild. Perhaps, the researchers suggested, the elephants wouldn't use the sticks to pull down the food (though they were quite happy to use them to, for instance, scratch themselves) because, in those situations, they'd rather use their trunk to feel about, and you can't do that when you're holding something in it. Previous studies on elephants had suggested that, for all their remarkable intelligence in other areas, true problem-solving insight was beyond them. Maybe we just weren't using the right tests.

Two New Rodents
Not all new species reports are as exciting as a new dolphin, but even so, you might be surprised at how common they are, even among mammals - as opposed to, say, insects, where there must be a vast array of beetles and so forth out in the jungles that we haven't seen yet. The June issue of the Journal of Mammalogy reports two potentially new species. Dolphins aside, I've mentioned before how fraught this can be, and there's a lot of argument over what a species actually is, let alone how to find one, so we can't be sure these will stand the test of time, but I think they're still worth looking at.

The first comes from India. Here we have what appears to be a subspecies of the familiar black rat, also called the ship rat, house rat, and so on, and second only to the slightly larger brown rat in its ability to follow humans around the globe. Unlike the other black rats nearby, this subspecies has a white belly, but its otherwise pretty much identical. Nonetheless, French researchers have concluded, after an examination of their genetics and biochemistry that they are not merely a subspecies, but an entirely separate species, living alongside the 'real' black rats in the dense forests of the Nilgiri Hills. There is, they argue, no evidence that the two interbreed, despite having every opportunity to do so - presumably, they have a better method than blood-testing to tell each other apart.

The second species, Cerradomys goytaca, is a type of marsh rat from the coasts around Rio de Janeiro. It looks pretty much like any other rat, although, like most rats and mice native to the Americas, its actually a member of the hamster family. Although the researchers do report distinctive genetics, they also provide a detailed physical description that makes it possible to tell the animal apart from all of its related neighbours. It is slightly larger, with a wider snout and thinner hair than any of the three species already known, and inhabits shrubby subtropical forests along a relatively narrow stretch of the Brazilian coastline.

New Fossils Reported
I'll admit it - two of these are rodents as well, although neither of them are rats. The first is a ground squirrel that lived, around seven million years ago, on the north shores of Lake Chad - then much larger than it is now. It appears to have died when its burrow collapsed, possibly in a flood, and the shape of its teeth suggests that it would have eaten hard fruit, presumably in an open forest or savannah environment. It's significant because it would have lived alongside Sahelanthropus, the oldest known member of the African ape subfamily to which we ourselves (along with chimps and gorillas) belong. Being able to tell how this squirrel lived therefore gives us some insight into the environment of one of our own early relatives.

From about a million years later, and far away in Myanmar, comes a fossil porcupine. All they have is a small piece of the lower jaw, but even that shows that the animal would have been larger than any other known porcupine in the area (unless it had a particularly large head, which seems unlikely). The shape of its teeth suggest an adaptation to an increasingly dry habitat, dominated by grassland, unlike the jungles of today, something that fits with our understanding of past climate change in the area.

Rather more dramatic, perhaps, is a far older fossil, of an animal that lived in Wyoming as much as 40 million years ago. Again, we only have a jaw, although that's nearly a foot long, which suggests a fair-sized animal. The jaw probably belongs to some sort of tapir-like creature, although its sufficiently odd that that's difficult to say for sure. It doesn't seem to be closely related to anything else that we know of, and perhaps represents some otherwise lost lineage only distantly related to the true tapirs.